This invention relates to a novel and improved convenience end for metal containers and the like, and more particularly relates to convenience ends of the type adapted for use with beverage or beer containers in which a gate panel or push tab is formed out of the wall of the end closure to form a separable opening therein.
Sheet metal containers typically used for food and beverage products have a generally cylindrical body portion and an end closure at each end to close off and seal the contents within the container. Innumerable approaches have been taken in the formation of openings in one end of the container for removal of the contents. In recent years, for example, beer and soft drink cans have tear portions or gate panels formed in the wall of one end of the can which can be selectively severed or otherwise separated from the end to form the opening therein. Representative end closures of this type are set forth in U.S. Pat. to Klein No. 3,779,417 for FLEX TAB FOR A GATED CAN LID and DeLine et al No. 3,794,206 for FRANGIBLE OPENING MEANS FOR A CONTAINER LID, assigned to the same assignee of this invention. In each, the line of weakening or separation between the gate panel and rest of the end closure is formed in the outer protective edge, commonly referred to as the triple fold, along a section outwardly of the opening, and inward pressure is applied to the gate panel in order to cause its separation from the end. A number of advantages are realized in the use of a triple fold along the juncture of the gate panel and rest of the end closure, most notably the protective bead formed along the drinking edge of the can and substantial reduction in metal required in forming the entire end as well as overall economy in manufacture and formation of the gate panel in the least number of steps. Moreover, the gate panel can be formed out of aluminum or steel and constructed in such a way as to form an effective seal with the end closure and to withstand the pressure of its contents; yet can be easily opened by inward manual pressure applied by the finger or thumb.
The aforementioned patent to Deline et al alludes to the advantages of combined coining or thinning of the triple fold or bead section followed by scoring same in forming the line of separation between the gate panel and lid. However, in mass production of lids there is a practical difficulty in maintaining close tolerances in coining or scoring the triple fold under repeated operations principally due to the tendency of the edge of the scoring punch to become dulled after repeated use. It is therefore highly desirable that the triple fold or bead be formed in such a way as to assure uniform thickness along the line of separation to be formed as well as to form the line of separation or weakening in such a way as to assure a continuous line of separation in each gate panel formed without necessity of constantly replacing or sharpening the tools.
Furthermore, it has been found that selective formation of stiffening areas in combination with the line of separation formed as described will afford much greater ease of opening, particularly initial severance of the gate panel away from the end closure. Moreover, it is desirable to form the gate panel in such a way as to provide for the widest possible opening size at the leading end of the pour opening as well as ease of separation of the panel away from the lid merely under finger pressure so that the gate panel can be displaced inwardly into the interior of the can.